The present invention relates to a disk drive, such as a hard disk.
In recent years, hard disks have been mounted in various types of equipment, expanding their application areas. Under these circumstances, a number of techniques are proposed to increase information recording capacity, while promoting further reduction in size of the hard disk itself. Among these, a method is typically known, in which data tracks are recorded like a shingle roof such that part of adjacent data tracks is overwritten sequentially from an inner to outer circumference of a recording medium (the method will hereinafter be referred to as a shingle write method). This achieves data tracks, each being narrower than a recording width a magnetic head actually writes.
The aforementioned method, however, involves a problem. Specifically, when, for example, data is written in a k-th data track as counted from the inner circumference, it is necessary to rewrite all data tracks covering from the k-th one to the outermost circumference. To reduce an overhead of this need of rewriting, Patent Document 1 (U.S. Pat. No. 6,185,063) discloses a technique as detailed in the following.
Specifically, in the technique disclosed in Patent Document 1, two data tracks are paired up to form a group and recording is performed within this group through the shingle write method. More specifically, of the two data tracks included in the group, the data track on the inner circumference side is recorded and then the data track on the outer circumference side is recorded. Part of the data track on the outer circumference side is not overwritten and the data track on the outer circumference side is one having a recording width of the magnetic head.
The technique disclosed in Patent Document 1 permits relatively flexible rewriting of data. Specifically, a read position is varied between odd-numbered data tracks and even-numbered data tracks. This allows the read position to be set by avoiding an overwriting portion (an overlapping portion) of the data tracks paired up into a group (see FIG. 10 of Patent Document 1).